Protective covering for resistance-conductors.



UNIT

stares PATENT OFFICE.-

DY, NEW YORK, ASSIGNOR' TO GENERAL ELECTRIC COMPANY, A CORPORATION OFNEW YORK.

JOHN T. H. DEMPSTER, OF SCHENECTA PROTECTIVE COVERING FORRESISTANCE-CONDUCTORS.

No Drawing.

To all 1137mm it may concern Be it known that l. Jon's T. ll. Dunns'rnn, a citizen of the United States, residing at- Schenectady. countyof Schenectady. State of Yew York. have invented certain new and usefulimprovements in lrotective Coverings for RtSlSltllltQlOlltlllt'tlllS. otwhich the following is a specification.

This invention relates to means For protecting resistance conductorswhich are used in electric heaters and the like and has for its objectthe provision of a covering or protective. layer which will prevent theinjurious action of certain resistance conductors. whenheated. upon theinsulating material which is in contact therewith.

in the construction o't electricheaters the like, high resistanceconductors are trequently used containing metal which t'orms an oxid onthe conductor. This oxid has been tound in some cases to attack the micaor other insulating material which is placed in contact with it when theconductor attains a hightemperature. This is particularly true otcertain resistance coinluctors containing iron. as tor instance. analloy of iron. nickel. and chromium. resistance conductor o'l thiscomposition. when heated. Forms an oxid or scale which has heen found tocomhin with mica to term a very low melting point mixture. l have toundthat he applying a coating ot a mixture which is hasic in character thisaction hetweeu the oxid and the mica can he prevented.

In carrying out my invention. l apply pret'eral'ily to the surl'ace otthe mica, although ot course the coatingma he applied to the resistanceconductor. a coating composed of a basic oxid with an aluiuiuate and ahinder. This hinder may he ol such 1 nature as to make a glutinousmixture like paint, so that the material may he laid on with a hrush.The particular composition which I have l'ound to he very satisfactoryis a mixture of of an oxid of aluminum, magnesium. zinc. or chromiumandv 50% sodium aluminate. This is mixed with enough dextrin and waterto Specification of Letters Patent. Application filed Marchfit), 1909.Serial No. 484,772.

and

Patented June 4, 1912.

make a thick cement or paste. The components of this compound, beinghasicin character, will not slag with the oxid on the conductor. Thesodium aluminate reduces the melting point somewhat. which is still veryhigh. and ,the dextriu furnishes a small amount ot'icarhon when heatedand preventsv the initial oxidation of the conductor.

ltv is evident of course. that other materials may he used and theproportions varied. it" desired. since I have merely se torlh aparticular and specific compound in accordance with the patent statutesfor purposes ol' illustration. and various modifications thereof willsuggest themselves, to those skilled in the art without departing fromthe spirit ol my invention, theyscope ot' which is set torth in theannexed claims.

What I claim as new and desire to secure h v Letters Patent of th UnitedStates. is,-

.l. The comhination ot anoxidizable resistance conductor. a micainsulation adjacent thereto. and a protective material interposedhetween the conductor and the mica. said naterial comprising a basicoxid.

3. The comhination of an oxidizable resistance conductor. a micainsulation adjacent thereto. and a protective material interpo edhetweeu the conductor and the mica, said material comprising aluminummid and an aluminate.

I). The comhiuation ot an oxidizahle resistance conductor. a micainsulation adjacent thereto. and a protective material interposedhelween the conductor and the mica, said material comprising aluminumoxid, an aluminate and a hinder.

l. The comhination of a resistance conductor containing iron, nickel,and chr0- mium. a mica insulation adjacent thereto, and a protectivematerial between the conductor and the mica said material comprisinaluminum oxid and an aluminate.

In witness whereof, I have hereunto set; my hand this 19th day of March,1909, i

JOHN T. H. DEMPSTER.

\Vitnesses:

Henna Onroim, irlAno-unrr E. \Voomacr.

